High energy explosive compositions and method of preparation

ABSTRACT

A dense explosive composition of extremely high energy and relatively high detonation velocity, with relatively long sustained application of high disruptive force, comprises a concentrated solution of ammonium nitrate, high proportions of finely divided aluminum, relatively small proportions of water, and a small amount of special combinations of cross-linking and thermally stable thickeners. The composition is prepared at elevated temperature, mixed very briefly, and delivered or packaged by pumping from mixer to receptacle where it sets up quickly. Density and sensitivity may be controlled by incorporating gas or porous inert filler material.

United States Patent Cook et al. [4 1 Apr. 25, 1972 [541 HIGH ENERGYEXPLOSIVE 3,330,706 7/1967 Griffith 149/60 x COMPOSITIONS AND METHOD OF3,457,126 7/1969 Travers et al. ..l49/44 X PREPARATION Melvin A. Cook;Lex L. Udy, both of Salt Lake City, Utah Intermountaln Research 81:Engineering Company, Inc.

Apr. 25, 1969 inventors:

Assignee:

Filed:

'Appl. No.: 819,248

US. Cl. ..149/2, 149/43, 149/44,

References Cited UNITED STATES PATENTS Colegrove 149/44 X PrimaryExaminer--Carl D. Quarforth Assistant Examiner-Stephen J. Lechert, Jr.Anorney-Edwin M. Thomas [57] ABSTRACT 7 Claims, 1 Drawing FigureIIIGI-IENERGY EXPLOSIVE COMPOSITIONS AND MET'I'IOD OF'PR'EPARATIONBACKGROUND AND PRIOR ART ln U.S. Pat. No. 2,836,484 Streng andKirshenbaum describedan explosive composition made up of 38 to49 percentby weight of particulate aluminum, 20 to 43 percent of a stableoxidizer'su'chas ammoniumnitrate or analogous oxidizer selected from theinorganic'nitrates, perchlorates, etc., and enough'watenabout 28percent,to'bring-the aluminumwater ratio into a range of 1.4 to L5. Intheir compositions there was enough water to fully dissolve theoxidizer. The aluminum content, particularly if it should consist ofvery finely ground aluminum, issohigh as to make its dispersion into anaqueous liquid extremely difficult. Accordinglynhe inventors in said"patent suggested use of emulsifyingagents tozhelp disp'erse thefinelydivided metal. However, emulsifying agents are often objectionable inslurry explosives because they may cause extensive desensitization.

lt-is' possible, when very large proportions of fine aluminum are used,thatthe particles may support each other mechani cally. Insuch a case,there is no trueslurry.'By definition, a slurryis a suspension of solidparticles in a liquid. Unless such a large quantity of solids is usedthat the particles support each other against gravity, they will notlong remain suspended in an unthickened or non-viscous medium as asimple aqueous solution-of ammonium nitrate. For this reason,'the priorart has found it necessary to gel or otherwise thicken the liquid phase;otherwise, segregation of the solids by gravity'occurs and thecomposition will fail to detonate. Gellingagents of the prior art,-suchas guar gum, starch, etc., with or without crosslinking agents usuallydo not retain their high initial'viscosity, particularly during extendedstorage under severe temperature conditions. For military use suchcompositions must: be mechanically as well as chemically stable overtemperatures ranging from well below freezing to tropical and desert suntemperatures-of 130 F. and even up to 160 F .One aspectof this inventionis to provide such storage stability.

Highbrisant explosives suchas TNT are employedin militaryshells, bombs,etc., for use on hard targets such as concrete and steel structures,vehicles, etc., where an extremely high shattering effect ator very nearthe center. of detonation is needed. The impact of the projectile andits detonation must be at or very close to such structures to beeffective..TNT has a detonation velocity of about 7,000 meters persecond and under favorable conditions it develops a detonation pressureas high as 2,250,000psi, or'more.

Cyclotol", formedby slurrying granular RDX in molten TNT and casting thecharge, produces even greater detonation pressures than TNT.Compositions of this type have also been combined with certainproportions of finely divided aluminum, to increase their energy andtherby obtain very high brisance or shattering power.

While these conventional military explosives are suitable for hardtargets at close range, they are less suitable where a wider area blasteffect of at least fairly high intensity is desired. In order to destroysofter targets over a much larger area, the blast duration must beprolonged considerably. The energy of conventional high brisanceexplosives is expended in a very brief period of time. Hence, althoughthe peak pressure exerted may be very high, a pressure destructive tosoft targets is not sustained for as long as is desirable to accomplishdestruction or demolition of relatively softer targets farther from thedetonation point.

One of the objects of the present invention is to make available anexplosive composition which approaches the high brisance or detonationblast effect of TNT but which also begins to approach the area blastingeffect, e.g., of an atomic bomb. An important aspectof the presentinvention is the discovery that viscous gel or slurry type explosives,based on powerful inorganicoxidizer salts, combined with large quantities of metallic aluminum, have the above described area blastingeffects to a good degree.

primarily on combinations of one or more of the powerful oxidizer saltsnamed above, with fine, particulate 1 aluminum,

using water to establish a substantially continuous liquid phase. Minorquantities of other ingredients such as stabilizers, thickeners, gassingagents, etc., are known.- Guar gum and other gelling agents and/orstarches which may or may not be cross-linked, have been used asthickeners along with borax, dichromates, etc., which accelerate oraugment the desired thickening action.

Compositions of-the types just described above have gone into wide usefor blasting, particularly in hard rock mining, large scale rockexcavation, etc. In some cases, self-explosive materials such as TNT ingranular form have been combined with these slurrieswith good results.It is known that some of these agents have a higher total energy Q thancomparable weights of TNT, etc.

In general, aluminized slurries based on ammonium nitrate, or on acombination of ammonium nitrate and sodium nitrate, and analogousoxidizers, have moderately high detonation velocities. Sincethey can beprepared in the field, by mixing the relatively safe ingredientstogether at or near the site of use,'they have. definitesafety-advantages. They normally are thickened somewhat but are liquidor semi-liquid in nature, at least when first prepared, so'they can bepoured or pumped directly into boreholes, packages or other receivers.

Streng-and Kirshenbaum have suggesteduse of 38 to 49 percentaluminum.Cook andFarnam U.S. Pat. No. Re 25,695, mentioned above,showedlowerproportions of water'than suggested by'Streng and Kirshenbaum andsuggested that the slurry, with continuous liquid phase, should be socomposed rganic oxidizer ofthenitrate type (ammonium nitrate or mixturesthereof with sodium nitrate), can be introduced into a water-filledborehole and remain there undiluted for several days.

The :use of thickeners is highly advantageous for stabilizing suchmaterials in' the presence of ground water in boreholes, for example.

The compositions thus described in the prior art have become the basisfor current large-scale and successful use of blasting slurries. Most ofthem have hadrelatively low aluminum content, up to 15 to 20 percent byweight, but usually less.

Prior to the present invention it has not been the practice to use morethan about 20 percent of aluminum, or 25 percent at most in slurries.There are several reasons for this. Aluminum is one of the mostexpensive ingredients in blasting compositions of the slurry type. Iffinely particulated, it is quite reactive with water. While somepublications or patents mention use of more than 20 or 25 percent ofaluminum, e.g., U.S. Pat.

Nos. 3,307,986; 3,303,074; 3,377,909, and 3,214,307, the art simply hasnot found it desirable in practice, or economical, to useso much.

Aluminum, particularly in the finer grades, such as paint or pigmentgrades, is hard to disperse in aqueous systems in large proportions andfor good sensitivity it is preferable that the aluminum be notcompletely wet by the aqueous phase. See Clay et al., U.S. Pat. No.3,249,474.

For the above reasons, it is surprising to discover that a thickenedslurry of very high aluminum content but low water content, andthickened in an unusually stable manner, has several particularadvantages. The explosives of this invention have extremely higher totalenergy than TNT. They are relatively inexpensive. They can be made up inthe field, using critical proportions of known major ingredients.Further improvements are obtained by the use of carefully chosenproportions of particularly effective thickeners having propertiesespecially suitable for the needed physical properties of the slurry.

The explosives of the present invention are particularly suitable forarea blasting, especially against relatively wide areas of targetssofter than concrete or steel. These compositions are effective againstsuch targets or target areas at greater distances from the explosioncenter than prior art explosives. It will be understood, however, thatthe compositions of this invention also are highly useful for industrialand other uses.

On a pressure-time graph the new compositions exhibit slightly lowerpressure peaks than TNT at points very close to the center ofdetonation. However, while the pressure curve for TNT drops rapidly tozero from its peak, compositions of the present invention show apressure vs time curve, which is somewhat lower initially than that forTNT, but which maintains a relatively high level for a much longerperiod of time. The result is that the area under the curve, which is ameasure of delivered total energy, is very substantially greater for thenew slurry explosive than that for TNT. This is true, in general, notonly for TNT but for other explosives of the prior art including thosediscussed above.

SUMMARY A high Q" explosive of reasonably high detonation velocity andoutstanding area blasting properties, effective especially against soft"targets, is made up of ammonium nitrate, enough water to make a stiffslurry, and 32 to 43 percent by weight of finely divided metallicaluminum. A special thickener composed of xanthan gum and cross-linkedguar gum (or starch) gives good storage stability under extremetemperature conditions.

BRIEF DESCRIPTION OF DRAWING The single FIGURE of drawing showsgraphically a pressure vs. time graph comparing cast TNT with thecomposition of this invention.

DESCRIPTION OF PREFERRED EMBODIMENT The invention will now be describedwith reference to specific examples.

EXAMPLE 1 A composition was made up of the following ingredients inpercentage by weight:

Ammonium nitrate 50.0

Particulate aluminum,

finely divided 350 Water l4.0

Thickener-stabilizer X (described below) 1.0

Total: [00.0

From its inclusion of such a high percentage of aluminum, and the factthat its oxygen balance was about -22 percent, one would expect thatthis particular composition should not have the extremely high blastingpower needed for wide area blasting of the type described above. Thiscomposition proved to be extremely powerful in tests, as will be shownbelow. The process of preparation was as follows:

The pre-mixed aluminum and the thickener (which in this case was acombination of a specially treated self cross-linking gum with a smallamount of ammonium phosphate, to inhibit water-aluminum reaction) weremetered into a mixing funnel. In the funnel these were blended with asaturated water solution of ammonium nitrate in proportions to form athin slurry with the aluminum. This slurry was thickened, thereafter, by

adding dry prills of ammonium nitrate to bring total ammonium nitrate upto 50 percent. The slurry as thus compounded was mixed for a few secondsto make it smooth and homogeneous. Then it was pumped immediately,before the thickener became fully effective, and forced continuouslythrough a length of rubber hose to the point of use. At the time ofdelivery, about 30 seconds after combining the ingredients, the slurrywas still reasonably fluid and was still pumpable. with a viscosity inthe neighborhood of about 3,000 centipoises. After this pump-deliveredslurry had set for IS minutes, the cross-linking reaction of thethickener had developed sufficiently that the entire slurry mass wasgelled to a stiff rubber-like consistency. After further setting ithardened or toughened somewhat further so that it approached theconsistency of an ordinary gum rubber eraser.

Because of its initial fluidity, this material can conveniently bepoured or pumped into bombs, for example. Choice of an effective, stablethickener is very important. Also, when the slurry thickens up to astiff rubbery consistency and retains such consistency, it can betransported in aircraft without concem for shifting of center ofgravity. Such a shift can cause a serious problem in transportation byair of less viscous or liquid slurries, particularly in bombs of largesize. The military uses intended for this explosive composition mayinvolve large bombs and analogous containers. For practical purposes,after the composition of Example I has set for a short time, it issubstantially as stable as a solid explosive, e.g., cast TNT, so far ashandling or shipment are concerned.

This composition was found not to be impact sensitive to standard30-calibre rifle bullets. Also, at 20 C., it was not sensitive to a No.6 electric blasting cap. The composition and all its ingredients arenon-toxic; hence, it can be handled without special clothingrequirements. If spilled, there is no dangerous contamination or hazardto personnel and the spills can readily be cleaned up with water.

EXAMPLE 2 Another quite similar but more viscous composition was made upof the following ingredients in percentage by weight:

Ammonium nitrate 49.55 Water 14.00 Aluminum 35.00 Thickening gums andstabilizer 1. 5

Total: l00.00

This product, after standing briefly, was a stiff slurry with a densityof about 1.50 grams per cc, a critical diameter for detonation of 2.5inches, a detonation velocity of about 5,275 meters per second, and atotal energy 0 of about 1,900 calories per gram. Its seismic strength,compared to TNT, on a weight basis, was 1.45. The material of Example 2does not detonate in a 2-inch capped steel pipe fired with a 30.06-calibre bullet from 25 yards distance.

The thickener used in Examples 1 and 2 was a combination of a smallamount of conventional guar gum dispersed in the aqueous solution tothicken it enough to hold finely dispersed gas bubbles, a small amountof a self-complexing guar gum which is a very effective slurrythickener, giving a rubbery structure, but of poor storage stability,and a small amount of a xanthan gum, obtained from General MillsCorporation, and understood to be derived by bacterial action frompolysaccharide materials, probably guar gum. The latter has a highlyeffective stabilizing effect so that the thickened gel retains itstough, rubbery structure over extended periods of storage time, even athigh temperatures. A small amount of boric acid, also used, tends toassist in cross-linking and also contributes to chemical stability inrepressing reaction between the fine aluminum and water.

The compositions of Examples 1 and 2 were tested for minimum boosterrequirements. Boosters were made up of molten 50/50 pentolitecomposition (50% PETN and 50% TNT) poured, i.e., cast, in a 1.95-inchdiameter steel tube with a wall one-fourth inch thick which served as acontainer for the booster.'An SO-grambooster failed to detonatethecomposition of Example 2 at 20 C. A 90-gram booster detonated the sameat 20 C. and a IOO-gram booster detonated it at 5 C.

Severalother formulations and'test results are indicated in the table.

Example Composition (percent by weight) 3 4 5 6 Mam oxldizer solution 4O 85. 55 E20 14 Guar g'u 0. 15 Ethylene glycol 0. 30 Guar gum(eross-linkin 0.0 Dry fuels (blended in solutio slurry):

Paint grade A1 1 0. 6O 0; 5 Atomized A1 34 34. 5 35 34. 5 Guar gum plusxanthan. 0. 9 0.9 0. 0 O. 0 Boric acid; 0. 4 0. 1. 0 4 0.1 Ingredientsadded to slurry:

Dry NH4NO3 13. 35 14 13. 30 13. 1 Styrofoam beads-. 0. 9 Density(gm./cc.) 1. 5 1. 50 *1. 26 1.25 Critical diameter (inches) 2.0 2. 5 2.02.0 Detonation velocity (m./sec.) 5, 275 5, 275 Minimum booster (50/50pentolite),

grams 30.06 rifle bullet sensitivity at yards in .2 capped steel pipe 1Not tested. 9 3 failures/3 shots. 3 Dctonntcs.

One general mixing procedure is given above. A preferred specific mixingprocedure is as follows:

1. Place the oxidizer solution and accompanying crystals in an aluminumor stainless steel pot of adequate size and heat until the crystals areall dissolved. It should not be necessary to exceed a temperatureofabout 50 C. for this purpose. Allow the solution to cool to betweenabout and C.

2. Add further dry oxidizer, preferably predominantly ammonium nitrate(but it may comprise sodium nitrate), to the solution and stir untiltheprills are evenly distributed. These remain in suspension inthesaturatedsolution. Depending on the temperature at which the solution is madeand/or slurryis-prepared, more or less, or in some cases no dry oxidizerwill be added, as will be obvious, since solubility varies widely withtemperature.

. Add the entire quantity of dry fuel to the above mix at one time andstir vigorously until all of the dry pre-mix is blended and thethickener renders the mix thicker. Total mixing time usually does notexceed one minute.

. Fill the testing containers with the mix as soonas possible aftermixing, otherwise; cross-linking will set on to such an extent that theslurry will not flow (approximately 2 minutes after thickening to thestage described in (3) above).

This procedure applies to the slurries which are not modified orlightened indensity by inclusion of filler material, such as particlesof foamed cellular polymer, specifically, foamed polystyrene in beadform, well known commercially as Styrofoam beads or equivalent inertmatter which does not detract from the explosive properties but reducesspecific gravity. When these are added, proportions are between 0.2

and 1.5 percent, preferably 0.5 to 1 percent. The preferred procedurefor mixing in the latter, as in Example 6 in the table, is as follows:

Heat oxidizer solution until all of the crystals are dissolved and adddry oxidizer as above in (l) and (2). Then add Styrofoam" beads and stiruntil they are .uniformly distributed throughout the mix. Add the entirequantity of dry fuel to the mix at one time-and stir as in (4) above.Then fillthe testing containers as described in (5) above.

In the composition of Example 6 the amount of dry oxidizer is reducedslightly to permit the use of Styrofoam" beads to obtain lowdensity. Theproduct is a highly aluminized low densityslurry. All componentsand theslurry'itself are stable and non-toxic. Example 6 was repeatedin-another 20-pound batch with'similar procedure and results. This'lowerdensity Density Critical diameter Minimum booster required 1.25 g per cc2.0 inches 20.0 g of 50/50 pentolite as compared with or 5 shown aboveIt detonates when fired with a 30.06-calibre bullet at 25 yards in a2-inch capped steel pipe. In this respect it is, of course, not quite assafe as the denser product.

One problem encountered in filling receptacles such as bombs with slurrycompositions which have been aerated to any substantial extent has beenthat of cavities. Such develop frequently in bombs and other containersafter filling. Probably because the slurries are necessarily aeratedsomewhat on mixing, shrinkage occurs which leaves the receptacle partlyunfilled especially after it stands for a while. This can be avoided byusing a procedurewhich involves fillingunder pressure. The details ofsuch procedure form no part of the present invention.

An effective composition is made up of the followingingredients, itbeingunderstood that variations in quantity of paint grade aluminumwillinfluence sensitivity to detonation.

EXAMPLE 7 Material Ammonium nitrate (AN),

Percentage by weight industrial grade prills 49.25 Water [4.0 Aluminum350 (a..atomized type 33-35) (b. flaked paint grade 0-2) Ethylene glycol03 Conventional guar gum 0.15 Cross-linking guar gum 0.3 Xanthan gum 0.9Boric acid 0.1

Total: l00.00

At various temperatures and pressures, the density of a slurry of thegeneral types described in examples above varied as follows:

Temp 'C. P. (psig) Vol. ml. Density 12 0 114.0 1.49 l 1 107.3 1.57 23106.0 1.61 49 104.0 1.64 45 21 "4.0 1.49 30 112.0 1.51 40 111.0 1.53 60110.0 1.54 80 109.5 1.55

Probe distance, (vet Peak, Impulse, Peak, Impulse, Peak, Impulse, Peak,Impulse, (ompnsition p.51 p.s.i.-ms. p.s.i p.s.i.-ms. psi. p.s.i.-ms.psi. 1).$.1.-l1lS.

'lN'l (average 017 tests). 80. 1 54. 8 21.6 16. G 8. 6 6. 10, 3 18. 6Example 1 (average 017 tests). 65. 7 52. 8 21. 7 18. 8 14. 6 25. 11. 111!. 5 Slurry 1I-1 (average 014 tests)" 62.7 411.2 15.11 15.5 7.1 8. 613.3 Slurry ll-2 (average 015 tests) 48. 7 13. 3 14.6 7. 6 8. 0 12. 2Slurry l- 2 (average of 7 ttSts) (i8. 3 45. 4 111.51 16.11 11.5 10.1 18.T Slurry 1-3(11V(lt1g0 017 tests). A 48. 9 3!). 5 14. 8 13. 0 7. (l A 8.3 1'1. 4

Compositions designated Example 1, H-1 and 1-2, respectively, were ofthe same general density range, i.e., 1.19 to 1.25 g/cc. Composition l-3was more dense, about 1.45 g/cc. The precise constituents ofcompositions 11-1 and 1-1-2 are not known. They were tested merely asrepresentative examples of known explosive slurries.

The composition of Example 1 gave lower pressure than TNT at feet, equalor slightly superior at 16 feet, greatly superior at 22 feet, andmoderately superior at 28 feet. Slurries 1-2 and 1-3 were aluminized,water-ammonium nitrate compositions containing respectively 25 and 10percent of aluminum.

It will be obvious to those skilled in the art that many variations maybe made in formulation without departing from the spirit of theinvention. For example, particles of self-explosive materials, e.g.,TNT, RDX, nitrocellulose, etc., may be added. An important aspect of theinvention is the discovery that a distinct optimum power, particularlysuperior for area blasting purposes, is obtained by combining about 45to 55 percent by weight of powerful oxidizer, preferably comprisingmostly or at least two-thirds ammonium nitrate, with 32 to 43 percent offinely particulated aluminum, part of which preferably is flaked paintgrade, using about 1 1 to 18 percent, preferably 13 to 16 percent,ofliquid ofwhich the major proportion is water. A substantial part ofthis liquid, however, may be a glycol, alcohol, ketone, aldehyde oramide. Such, if used, should be water soluble or at least watercompatible. A thickener must be used which is highly effective in lowproportions (preferably 0.5 to 1 percent, but proportions as high as 5percent may be used, especially where superior gel stiffness andstability are required for prolonged storage at high temperatures) tomake the slurry stiff, rubbery, and stable. Pre-gelled starch, whenused, may go as high as 2 percent. Gum-type thickeners are preferred andshould be strongly cross-linked. Proportions of 0.35 to 1.3 percent byweight are recommended.

For the stable highly viscous or rubbery consistency preferred forstorage and transportation, at least 0.5 percent of highly cross-linkedthickener preferably including a xanthan gum, should be included.Preferably, at least part of the thickener is added to the solutionbefore the insolubles are added. This aids in trapping large numbers offine gas bubbles in the solution, which materially aid in promotingsensitivity to detonation, even with very minor reduction in density.The thickener preferably is a polysaccharide, i.e., a starch or gum ofdelayed action type, so that the slurry can be pumped or poured for atleast a few seconds after mixing, but it also includes a component whichproduces high and lasting viscosity in the liquid phase. For thisreason, two components, i.e., cross-linking guar gum plus the xanthangum are preferred. This combination thickening system is particularlyimportant when the gel is to be stored for extended periods. It isstable at temperatures which may range from well below freezing to asmuch as 160 F. and for periods ofa year or more.

In a typical case the composition may contain about 10 to percent of theoxidizer in solid state. It is insoluble, not by nature but by reason ofthe pre-saturation of the solution. For this particular compositionammonium nitrate is preferred as the oxidizer but up to 25 percent ofsuch oxidizer may be sodium nitrate.

As shown in the drawing which is based on the data of Example l andother compositions given in the above table, the

composition of this invention was outstanding in its performance atdistances of 16 to 28 feet from the center of the explosion. The areabounded by the rectangle ABCD was regarded by the testing party as oneof prime importance. TNT started high but dropped to a low pressure of8.6 psi at 22 feet, as compared with 14.6 psi for a typical compositionof this invention. Composition [-2 was a standard rock-blasting slurryof good quality for mining purposes. Composition 1-3 was a relativelyinexpensive slurry of low aluminum content. With TNT, there was smallincrease of pressure at a distance of 28 feet over that at 22 feet,probably due to ground reflection of pressure waves.

It will be obvious that reasonable variations in the composition, in itscomponents, and in proportions of various ingredients may be made bythose skilled in the art without departing from the concept and spiritof the invention.

What is claimed is:

1. An explosive composition in the form of a highly viscous, near solidaqueous slurry stable for storage under wide temperature ranges, with anormal density of at least about 1.5 grams per cc and having highbrisance and substantially greater total energy than an equal weight oftrinitrotoluene, comprising the following ingredients in percentage byweight, based on the total composition:

a. 45 to 55 percent of powerful inorganic oxidizer, of which at leasttwo-thirds is ammonium nitrate,

32 to 43 percent finely divided particulate aluminum,

13 to 16 percent ofliquid of which the major part is water and thenon-aqueous liquid is organic and water-compatL ble,

. a highly stable gelling and thickening agent for said liquid including0.1 to 2 percent, based on total composition, of a material selectedfrom the group which consists of pregelled starch and cross-linked guargum, and a supplemental quantity of xanthan bacteria modified gum as afurther thickener and high temperature viscosity stabilizer,

said slurry being pumpable before the thickening agent becomes fullyeffective but thereafter becoming a sub stantially solid elastic gelmass containing large numbers of very finely divided gas bubbles trappedand held in place by the viscous gel so as to substantially increase thesensitivity of said slurry.

2. Composition according to claim 1 wherein the thickener comprises 0.1to 0.5 percent of guar gum combined with a small amount of xanthan gum.

3. Composition according to claim 1 wherein the thickener comprises amajor proportion of a xanthan gum.

4. Composition according to claim 1 wherein there is added an inertfiller material in proportions of0.2 and 1.5 percent by weight, based onthe total composition, to reduce composition density.

5. Composition according to claim 4 wherein the inert filler materialcomprises particles of foamed polystyrene plastic solid.

6. Composition according to claim 5 containing 0.5 to 1 percent offoamed polystyrene plastic solid beads.

7. The process of preparing an explosive slurry blasting compositionwhich comprises, in combination, the steps of:

a. forming a saturated aqueous solution of powerful inorganic oxidizerof which a major proportion is ammonium nitrate;

0. blending into the solution about 32 to 43 percent by weight, based onthe total composition, of finely divided metallic aluminum, the finalcomposition containing 13 to 16 percent of liquid of which at least themajor part is water,

d. also blending into said solution at least 10 percent of powerfuloxidizer in addition to that in solution in the liquid, said additionaloxidizer being primarily ammoni um nitrate, to bring the total oxidizercontent of the composition to 45 to 55 percent by weight, and

e. stirring the composition to a smooth blend and discharging it to areceptacle before the thickening agent becomes fully effective.

i i IF

2. Composition according to claim 1 wherein the thickener comprises 0.1to 0.5 percent of guar gum combined with a small amount of xanthan gum.3. Composition according to claim 1 wherein the thickener comprises amajor proportion of a xanthan gum.
 4. Composition according to claim 1wherein there is added an inert filler material in proportions of 0.2and 1.5 percent by weight, based on the total composition, to reducecomposition density.
 5. Composition according to claim 4 wherein theinert filler material comprises particles of foamed polystyrene plasticsolid.
 6. Composition according to claim 5 containing 0.5 to 1 percentof foamed polystyrene plastic solid beads.
 7. The process of preparingan explosive slurry blasting composition which comprises, incombination, the steps of: a. forming a saturated aqueous solution ofpowerful inorganic oxidizer of which a major proportion is ammoniumnitrate; b. including at least a small amount of delayed actionthickener in said solution prior to addition of insoluble ingredientsthereto, and including in the total thickener ingredient a delayedaction thickener material selected from the group which consists ofpregelled starch and cross-linked guar gum and also a supplementalquantity of a xanthan bacteria modified gum, the total thickenerconstituting 0.1 to 2 percent by weight, based on the total compositionand being sufficient to gel the whole composition to a stiff, rubberyconsistency which is viscosity stable at high temperature; c. blendinginto the solution about 32 to 43 percent by weight, based on the totalcomposition, of finely divided metallic aluminum, the final compositioncontaining 13 to 16 percent of liquid of which at least the major partis water, d. also blending into said solution at least 10 percent ofpowerful oxidizer in addition to that in solution in the liquid, saidadditional oxidizer being primarily ammonium nitrate, to bring the totaloxidizer content of the composition to 45 to 55 percent by weight, ande. stirring the composition to a smooth blend and discharging it to areceptacle before the thickening agent becomes fully effective.